[clang][Driver] allow tilde in user config dir

[paperchalice]

Summary

This patch allows users to configure clang with option e.g. -DCLANG_CONFIG_FILE_USER_DIR=~/.config/clang or invoke clang with --config-user-dir=~/.config/clang.

[MaskRay]

clang/test/Driver/config-file3.c tests --config-user-dir= but I cannot think of a portable way testing this.
RUN: echo ~; %clang -### --config-user-dir=~ ... doesn't work as the selected directory is not dumped.

[paperchalice]

In D136940#3893391, @MaskRay wrote:

clang/test/Driver/config-file3.c tests --config-user-dir= but I cannot think of a portable way testing this.
RUN: echo ~; %clang -### --config-user-dir=~ ... doesn't work as the selected directory is not dumped.

I can dump user configuration file directory via clang --config-user-dir=<some directory> -v, but
RUN: { echo tilde: ~; %clang -v --config-user-dir=~ 2>&1; } | FileCheck %s -check-prefix CHECK-TILDE doesn't work on Windows.

[paperchalice]

I would appreciate if someone can commit this change.

[MaskRay]

In D136940#3893638, @paperchalice wrote:

I would appreciate if someone can commit this change.

I am waiting on @mgorny 's opinion for https://blogs.gentoo.org/mgorny/2022/10/07/clang-in-gentoo-now-sets-default-runtimes-via-config-file/

[mgorny]

I think you should be able to test it via overriding HOME envvar. I suppose you can limit the test to Unix.

[paperchalice]

Add test on Unix.

[mgorny]

Thanks. I haven't tested it but if it works for you and the test passes, LGTM.

@MaskRay, would you be able to test and push it? I don't have a recent clang build tree handy.

[paperchalice]

Ping @MaskRay

[mgorny]

Ah, I'm sorry for the delay. I have time right now, so I'll test and push it.

[MaskRay]

clang/test/Driver/config-file3.c

227

-### is missing. I fixed it in 37216b4b3aaab1fb293b7f628f8dd4999c0abb80

clang/lib/Driver/Driver.cpp

if ((!SysRoot.empty()) && llvm::sys::path::is_relative(SysRoot)) {
     llvm::sys::path::append(P, SysRoot);
     SysRoot = std::string(P);
   }
 
 #if defined(CLANG_CONFIG_FILE_SYSTEM_DIR)
   SystemConfigDir = CLANG_CONFIG_FILE_SYSTEM_DIR;
 #endif
 #if defined(CLANG_CONFIG_FILE_USER_DIR)
-  UserConfigDir = CLANG_CONFIG_FILE_USER_DIR;
+  {
+    SmallString<128> P;
+    llvm::sys::fs::expand_tilde(CLANG_CONFIG_FILE_USER_DIR, P);
+    UserConfigDir = static_cast<std::string>(P);
+  }
 #endif
 
   // Compute the path to the resource directory.
   ResourceDir = GetResourcesPath(ClangExecutable, CLANG_RESOURCE_DIR);
 }
 
 void Driver::setDriverMode(StringRef Value) {
   static const std::string OptName =
if (CLOptions->hasArg(options::OPT_config_system_dir_EQ)) {
           CLOptions->getLastArgValue(options::OPT_config_system_dir_EQ));
       if (CfgDir.empty() || getVFS().makeAbsolute(CfgDir))
         SystemConfigDir.clear();
       else
         SystemConfigDir = static_cast<std::string>(CfgDir);
     }
     if (CLOptions->hasArg(options::OPT_config_user_dir_EQ)) {
       SmallString<128> CfgDir;
-      CfgDir.append(
-          CLOptions->getLastArgValue(options::OPT_config_user_dir_EQ));
+      llvm::sys::fs::expand_tilde(
+          CLOptions->getLastArgValue(options::OPT_config_user_dir_EQ), CfgDir);
       if (CfgDir.empty() || getVFS().makeAbsolute(CfgDir))
         UserConfigDir.clear();
       else
         UserConfigDir = static_cast<std::string>(CfgDir);
     }
   }
 
   // Prepare list of directories where config file is searched for.

clang/test/Driver/config-file3.c

 // RUN: %t/testdmode/x86_64-unknown-linux-gnu-clang-g++ -m32 --config-system-dir= --config-user-dir= -no-canonical-prefixes --version 2>&1 | FileCheck %s -check-prefix FULL5-I386 --implicit-check-not 'Configuration file:'
 //
 // FULL5-I386: Configuration file: {{.*}}/testdmode/clang-g++.cfg
 
 //--- Test that incorrect driver mode config file is not used.
 //
 // RUN: rm %t/testdmode/clang-g++.cfg
 // RUN: %t/testdmode/x86_64-unknown-linux-gnu-clang-g++ --config-system-dir= --config-user-dir= -no-canonical-prefixes --version 2>&1 | FileCheck %s -check-prefix NO-CONFIG
+
+//--- Tilde expansion in user configuration file directory
+//
+// RUN: HOME=%S/Inputs/config %clang --config-user-dir=~ -v 2>&1 | FileCheck %s -check-prefix CHECK-TILDE
+// CHECK-TILDE: User configuration file directory: {{.*}}/Inputs/config